The oral and topical administration of zinc and zinc containing compounds have long been utilized in the treatment and prophylaxis of the common cold. For example, a number of patents have been issued to George A. Eby, III which disclose zinc containing compounds for treating the symptoms of, or curing, the common cold.
Eby's U.S. Pat. No. 4,503,070 issued in 1995 discloses the use of a lozenge containing zinc gluconate to reduce the duration of a cold and his U.S. Pat. No. 5,409,905 discloses a composition having a highly ionizable zinc compound which provides sustained release of Zn2+ ions. The highly ionizable zinc compound is selected from zinc acetate, zinc propionate, zinc butyrate, zinc betahydroxybutyrate, zinc benzoate, zinc formate, and mixtures thereof while the composition specifically excludes flavor masking amounts of anethole and strong zinc chelators.
U.S. Pat. No. 4,956,385 issued to Eby, III describes the method of applying an ionizable zinc compound other than zinc gluconate to the oral mucosa for treating the common cold. Later, in 1990, Eby's U.S. Pat. No. 4,503,070 was reissued as Re. 33,465 and included claims similar to Eby's '385 patent with the exception that the ionizable zinc compound was specifically identified and defined as being zinc gluconate.
Finally, U.S. Pat. Nos. 5,002,970 and 5,095,035 were issued to Eby, III in 1999 and 1992, respectively, which disclosed oral compositions for releasing zinc ions which included an anethole in an amount to flavor-mask the zinc aftertaste, or a sweet pharmaceutically acceptable carrier. Zinc gluconate, zinc acetate and zinc ascorbate were all identified as individual possibilities for the ionizable zinc compound used with an anethole while zinc acetate was identified as an ionizable zinc compound for use with a sweet pharmaceutically acceptable carrier.
Later, in 1997, two patents were issued to Bryce-Smith, namely U.S. Pat. No. 5,622,724 and U.S. Pat. No. 5,688,531, which disclosed nasal, oral and opthalmological sprays having a dilute solution of unchelated zinc ion for treating cold and allergy symptoms. Zinc sulfate and/or zinc chloride were specifically identified as acceptable selections for the unchelated zinc ion.
Still later, U.S. Pat. No. 6,139,864 was issued to Dun et al. in 2000. The Dun et al. patent describes foods and pharmaceuticals containing zinc and an antimicrobially effective amount of a sugar alcohol mixture. The zinc was identified as being present in the form of zinc gluconate or zinc acetate.
All of these patents disclose zinc compositions that include a single zinc compound as the source of zinc ions. Such compositions are thought to be deficient because the zinc compounds are generally configured to provide only slow release of zinc ions. Accordingly, improved methods and compositions for treating cold symptoms are desired.